Prior art nylon laminates may be prepared by a variety of methods including extrusion coating and coextrusion and the laminates may be either oriented or unoriented. When preparing an oriented nylon laminate, the usual prior art practice is to stretch the laminate at relatively high temperatures, in excess of 150.degree. F, and to perform orientation immediately after extrusion because nylon, after extrusion, will regain moisture which can impair its ability to orient. The effect of moisture on nylon is recognized in the prior art, e.g. in an article entitled "How To Extrusion Coat With Nylon" at page 125 of Modern Plastics magazine, July 1965, it is noted that a blanket of dry inert gas must be used to cover nylon granules in a hopper to prevent the nylon from absorbing moisture. Also, in U.S. Pat. No. 3,585,059 issued on June 15, 1971 to Daniel G. James, a waterproof coating is placed on a primed nylon substrate to protect the nylon from the water in a subsequently applied barrier coating dispersion thereby preventing wrinkling of the nylon substrate. In addition, U.S. Pat. No. 3,788,503 issued Jan. 29, 1974 to Hidenori Hirose et al keeps the water content of a poly-E-caproamide (nylon 6) film at not more than 2% while performing biaxial orientation. Accordingly, one object of the present invention is to produce a nylon laminate in which moisture is completely excluded from the nylon layer.
As mentioned above, the orientation of nylon laminates in prior art processes is usually performed at temperatures in excess of 150.degree. F and the orientation takes place immediately, i.e. within a few seconds or less. In departing from the teachings of the prior art, it has been discovered that a nylon laminate prepared by excluding moisture from the nylon layer may be oriented at temperatures below 150.degree. F and may be oriented either above or below 150.degree. F after a relatively long time lapse of up to 21/2 hours or somewhat longer. Thus, it is an object of the present invention to provide a nylon laminate which may be oriented at temperatures substantially below those taught in the prior art and in which the time lapse after quenching and before orientation is not critical.
In the prior art, when orientating a polyolefin/nylon laminate the olefin layers normally orient in the 13:1 to 25:1 biaxial stretching ratio or greater whereas nylon generally orients at biaxial ratio of about 6:1. However, in the process of the present invention, it has been surprisingly discovered that by orienting a nylon laminate wherein moisture has been excluded from the nylon layer that the olefin layers of the laminate will orient at the same ratio as the nylon layer. Accordingly, it is another object of the present invention to provide a nylon/olefin laminate in which all components of the laminate are oriented alike.
Still another object of the present invention is to provide a novel, improved, oriented film product comprising nylon 66 or a blend thereof with nylon 6.
The foregoing and other objects and advantages of the present invention will be readily appreciated by those skilled in the art from the following Summary of Invention.